Barack Obama filled in for Massachusetts Sen. Edward Kennedy at the Wesleyan Class of 2008 commencement Sunday, the Los Angeles Times reported. In a speech focusing on public service, Senator Obama invoked the Civil Rights legacy of the Kennedy-era and his own experience as a community organizer to a crowd estimated at 25,000. The families and friends of Wesleyan University’s 737 graduating seniors and 120 doctoral graduates shared the school’s sports field with Obama supporters who descended on Middletown, Conn., from around the region, spilling out onto a hill overlooking the field.

Mr. Obama invoked Wesleyan’s strong track record of students participating in community initiatives and serving in the Peace Corps, as he urged graduates to engage with their country’s ideals.

“You can take your diploma, walk off this stage, and chase only after the big house and the nice suits…. You can choose to narrow your concerns and live your life in a way that tries to keep your story separate from America’s,” he said.

“But I hope you don’t.”

Mr. Obama referred to himself as “pinch hitting” for Mr. Kennedy, originally scheduled to speak at commencement. The senator, who endorsed Obama in January, was briefly hospitalized for a seizure a week before the ceremony, and subsequently diagnosed with a malignant brain tumor. Early in the speech, Obama passed on a message from Senator Kennedy: “To all those praying for my return to good health, I offer my heartfelt thanks. And to any who’d rather have a different result, I say, don’t get your hopes up yet!”

On Tuesday the Boston Globe reported that on Memorial Day the senator, 76, was well enough to participate in the second leg of the Figawi boat race on Nantucket Sound. In his speech, Senator Obama said, “I have a feeling that Ted Kennedy is not done just yet.”